The U.S. is facing a dangerous epidemic in type 2 diabetes. Of the estimated 20.6 million individuals with diabetes, approximately thirty percent of them are undiagnosed. See, e.g., National diabetes fact sheet. Atlanta, Ga., Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, 2005. Another 54 million people have some form of pre-diabetes and many will progress to frank diabetes within three years. See, e.g., National diabetes fact sheet. Atlanta, Ga., Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, 2005; Cowie C C, Rust K F, Byrd-Holt D D, Eberhardt M S, Flegal K M, Engelgau M M, Saydah S H, Williams D E, Geiss L S, Gregg E W: Prevalence of diabetes and impaired fasting glucose in adults in the U.S. population: National Health And Nutrition Examination Survey 1999-2002. Diabetes Care 29:1263-8, 2006; Knowler W C, Barrett-Connor E, Fowler S E, Hamman R F, Lachin J M, Walker E A, Nathan D M; Diabetes Prevention Program Research Group: Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 346: 393-403, 2002. Numerous studies have shown that with early detection and effective intervention, diabetes can be prevented or delayed. See, e.g., Cowie C C, Rust K F, Byrd-Holt D D, Eberhardt M S, Flegal K M, Engelgau M M, Saydah S H, Williams D E, Geiss L S, Gregg E W: Prevalence of diabetes and impaired fasting glucose in adults in the U.S. population: National Health And Nutrition Examination Survey 1999-2002. Diabetes Care 29:1263-8, 2006; Knowler W C, Barrett-Connor E, Fowler S E, Hamman R F, Lachin J M, Walker E A, Nathan D M; Diabetes Prevention Program Research Group: Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 346: 393-403, 2002; Tuomilehto J, Lindstrom J, Eriksson J G, Valle T T, Hamalainen H, Ilanne-Parikka P, Keinanen-Kiukaanniemi S, Laakso M, Louheranta A, Rastas M, Salminen V, Uusitupa M; Finnish Diabetes Prevention Study Group: Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med 344:1343-50, 2001; DREAM (Diabetes REduction Assessment with ramipril and rosiglitazone Medication) Trial Investigators; Gerstein H C, Yusuf S, Bosch J, Pogue J, Sheridan P, Dinccag N, Hanefeld M, Hoogwerf B, Laakso M, Mohan V, Shaw J, Zinman B, Holman R R: Effect of rosiglitazone on the frequency of diabetes in patients with impaired glucose tolerance or impaired fasting glucose: a randomized controlled trial. Lancet 368: 1096-1105, 2006; Pan X R, Li G W, Hu Y H, Wang J X, Yang W Y, An Z X, Hu Z X, Lin J, Xiao J Z, Cao H B, Liu P A, Jiang X G, Jiang Y Y, Wang J P, Zheng H, Zhang H, Bennett P H, Howard B V: Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance: The Da Qing IGT and Diabetes Study. Diabetes Care 20:537-544, 1997; Chiasson J L, Josse R G, Gomis R, Hanefeld M, Karasik A, Laakso M; STOP-NIDDM Trail Research Group: Acarbose for prevention of type 2 diabetes mellitus: the STOP-NIDDM randomized trial. Lancet 359:2072-2077, 2002. In patients with diagnosed diabetes, other studies have shown that glucose control can lower the incidence of complications. See, e.g., The Diabetes Control and Complications Trial Research Group: The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med 329:977-986, 1993; UK Prospective Diabetes Study (UKPDS) Group: Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet 352:837-853, 1998.
Diagnosis is typically initiated during a physical exam with a primary care physician. However, current screening methods for type 2 diabetes and pre-diabetes are inadequate due to their inconvenience and inaccuracy. Specifically, the most widely applied screening test in the U.S., the fasting plasma glucose (FPG), has convenience barriers in the form of an overnight fast and a blood draw. FPG also suffers from poor sensitivity (40-60%) contributing to late diagnoses. See, e.g., Engelgau M M, Narayan K M, Herman W H: Screening for Type 2 diabetes. Diabetes Care 23:1563-1580, 2000. In fact, about one-half of diabetes patients present with one or more irreversible complications at the time of diagnosis. See, e.g., Harris M I, Eastman R C: Early detection of undiagnosed diabetes mellitus: a US perspective. Diabetes Metab Res Rev 16:230-236, 2001; Manley S M, Meyer L C, Neil H A W, Ross I S, Turner R C, Holman R R: UKPDS 6—Complications in newly diagnosed type 2 diabetic patients and their association with different clinical and biologic risk factors. Diabetes Res 13:1-11, 1990. A more accurate and convenient screening method could dramatically improve early detection of type 2 diabetes and its precursors, facilitating interventions that can prevent or at least delay the development of type 2 diabetes and its related micro and macrovascular complications.
Several studies including DCCT and EDIC have demonstrated that elevated skin advanced glycation endproducts (AGEs) are biomarkers of diabetes, highly correlated with the complications of diabetes and are predictive of future diabetic retinopathy and nephropathy. See, e.g., Monnier V M, Bautista O, Kenny D, Sell D R, Fogarty J, Dahms W, Cleary P A, Lachin J, Genut; DCCT Skin Collagen Ancillary Study Group: Skin collagen glycation, glycoxidation, and crosslinking are lower in subjects with long-term intensive versus conventional therapy of type 1 diabetes: relevance of glycated collagen products versus HbA1c as markers of diabetic complications. Diabetes 48:870-880, 1999; Genuth S, Sun W, Cleary P, Sell D R, Dahms W, Malone J, Sivitz W, Monnier V M; DCCT Skin Collagen Ancillary Study Group: Glycation and carboxymethyllysine levels in skin collagen predict the risk of future 10-year progression of diabetic retinopathy and nephropathy in the diabetes control and complications trial and epidemiology of diabetes interventions and complications participants with type 1 diabetes, Diabetes 54:3103-3111, 2005; Meerwaldt R, Links T P, Graaff R, Hoogenberg K, Lefrandt J D, Baynes J W, Gans R O, Smit A J: Increased accumulation of skin advanced glycation end-products precedes and correlates with clinical manifestation of diabetic neuropathy. Diabetologia 48:1637-44, 2005. A person with diabetes will accumulate skin AGEs faster than individuals with normal glucose regulation. See, e.g., Monnier V M, Vishwanath V, Frank K E, Elmets C A, Dauchot P, Kohn R R: Relation between complications of type 1 diabetes mellitus and collagen-linked fluorescence. N Engl J Med 314:403-8, 1986. Thus, skin AGEs constitute a sensitive, summary metric for the integrated glycemic exposure that the body has endured.
However, until the recent development of novel noninvasive technology to measure advanced glycation endproducts, a punch biopsy was required to quantify skin AGE levels. This method for “Spectroscopic measurement of dermal Advance Glycation Endproducts”—hereafter referred to as SAGE—measures skin fluorescence due to AGEs in vivo and provides a quantitative diabetes risk score based on multivariate algorithms applied to the spectra. See, e.g., Hull E L, Ediger M N, Brown C D, Maynard J D, Johnson R D: Determination of a measure of a glycation end-product or disease state using tissue fluorescence. U.S. Pat. No. 7,139,598, incorporated herein by reference. SAGE does not require fasting and creates no biohazards. It can automatically compensate for subject-specific skin differences caused by melanin, hemoglobin, and light scattering. The measurement time can be approximately one minute and thus can provide an immediate result.
The concept of quantifying dermal AGEs noninvasively was successfully tested in a previous in vitro study. In that work, concentrations of a well-studied fluorescent AGE, pentosidine, were accurately quantified in a porcine dermis model by noninvasive fluorescence spectroscopy. See, e.g., Hull E L, Ediger M N, Unione A H T, Deemer E K, Stroman M L and Baynes J W: Noninvasive, optical detection of diabetes: model studies with porcine skin. Optics Express 12:4496-4510, 2004. Subsequently, an early noninvasive prototype was evaluated in a diabetic vs. normal (case-control) human subject study, demonstrating that SAGE could accurately classify disease in a case-control population. See, e.g., Ediger M N, Fleming C M, Rohrscheib M, Way J F, Nguyen C M and Maynard J D: Noninvasive Fluorescence Spectroscopy for Diabetes Screening: A Clinical Case-Control Study (Abstract). Diabetes Technology Meeting, San Francisco, Calif., 2005, incorporated herein by reference.
A noninvasive method and apparatus for detecting disease in an individual using fluorescence spectroscopy and multivariate analysis has been previously disclosed in U.S. Pat. No. 7,139,598, incorporated herein by reference. Continued development of this method and apparatus has resulted in significant instrument and algorithm improvements that yield increased accuracy for noninvasively detecting disease, especially type 2 diabetes and pre-diabetes. The instrument improvements provide higher overall signal to noise ratio, reduced measurement time, better reliability, tighter precision, lower cost and reduced size compared to instruments disclosed in the art. The algorithmic improvements increase overall accuracy by more effective extraction of the information needed for accurate noninvasive detection of disease using fluorescence spectroscopy. These instrument and algorithm improvements are described herein, and have been tested in a large clinical study also described herein.